Support is requested for the establishment and maintenance of a multidisciplinary center for the study of immunologic mechanisms which may play a role in the pathogenesis of certain cutaneous diseases. Such a center will harness the combined efforts of dermatologists, immunologists and allergists from various departments in the University of California, San Diego. This application is directed to three areas of research relevant to skin diseases: (a) Immunoregulatory mechanisms in patients with a variety of skin diseases thought to be immunologic in nature, (b) metabolic and biochemical alterations in immunologically damaged skin and (c) regulation of cell traffic in the epidermis and relation to the Langerhans cell. Because of their prevalence and relevance, the specific diseases to be studied include leukocytoclastic vasculitis, drug eruptions, urticaria and atopic dermatitis. Cutaneous phototoxic reactions mediated either by drugs or by endogenous phototoxic chemicals (prophyrias) offer excellent models to study tissue damage produced by activation of the complement system and the subsequent release of chemical mediators. The question of whether Langerhans cells have a "trophic" function for lymphoid cells will be investigated. Its role in vivo will be evaluated by assessing its involvement in a variety of skin diseases in which a cell-mediated immunologic mechanism seems to be involved. These studies may help not only to further our knowledge in this area, but will serve in the development of new therapeutic approaches.